#!/usr/bin/env /usr/bin/python3
"""Launch the DSH desktop pet.

Detaches by default. A desk pet that dies with the terminal you started it from
is not a desk pet, it is a foreground program that happens to be shaped like
one — and leaving a window open just to keep it alive is exactly the friction
this is meant to remove.

    ./bin/dsh-macos-pet              # start in the background and return
    ./bin/dsh-macos-pet --stop       # stop the running pet
    ./bin/dsh-macos-pet --foreground # stay attached (logs to this terminal)
    ./bin/dsh-macos-pet --probe      # diagnostics, no window

Everything else is passed through to `dsh_macos_pet.app`.
"""

from __future__ import annotations

import os
import signal
import sys
from pathlib import Path

ROOT = Path(__file__).resolve().parents[1]
SRC = ROOT / "src"
if str(SRC) not in sys.path:
    sys.path.insert(0, str(SRC))

from dsh_macos_pet import bridge  # noqa: E402
from dsh_macos_pet.app import main  # noqa: E402

LOG = Path.home() / ".dsh-macos-pet" / "pet.log"


def stop() -> int:
    pid = bridge.live_pid()
    if pid is None:
        print("no desk pet is running")
        return 0
    try:
        os.kill(pid, signal.SIGTERM)
    except OSError as exc:
        print(f"could not stop pid {pid}: {exc}")
        return 1
    print(f"stopped desk pet (pid {pid})")
    return 0


def detach() -> None:
    """Double-fork into the background, with output going to a log file.

    Double, not single: the first fork lets the shell reap its child
    immediately, and `setsid` in between detaches from the controlling
    terminal so closing the window cannot take the pet with it.
    """

    if os.fork() > 0:
        os._exit(0)
    os.setsid()
    if os.fork() > 0:
        os._exit(0)

    LOG.parent.mkdir(parents=True, exist_ok=True)
    with open(os.devnull, "rb") as devnull:
        os.dup2(devnull.fileno(), sys.stdin.fileno())
    # Truncate rather than append: the interesting log is always the last run's.
    with open(LOG, "wb") as log:
        os.dup2(log.fileno(), sys.stdout.fileno())
        os.dup2(log.fileno(), sys.stderr.fileno())


if __name__ == "__main__":
    argv = sys.argv[1:]
    if "--stop" in argv:
        raise SystemExit(stop())

    foreground = "--foreground" in argv
    argv = [arg for arg in argv if arg != "--foreground"]
    # Diagnostics print to the terminal and exit; detaching would hide them.
    # `--install-skin` must not detach either: the agent that invoked it needs
    # the exit code and the message, and a backgrounded install would report
    # success before it had validated a single frame.
    # Split on '=' first: argparse accepts `--install-skin=mycat`, and matching
    # the whole token missed it — the install then fell through to the normal
    # launch path, which refuses to start when a pet is already running (the
    # usual case) or detaches and reports success without installing anything.
    inspects = any(
        arg.split("=", 1)[0] in ("--probe", "--inventory", "--install-skin",
                                "--skin-sheet", "-h", "--help")
        for arg in argv)

    if not foreground and not inspects:
        if bridge.live_pid() is not None:
            # Say so from the foreground; after detaching nobody would see it.
            print(f"a desk pet is already running (pid {bridge.live_pid()})")
            raise SystemExit(3)
        print(f"desk pet started in the background; log: {LOG}")
        detach()

    raise SystemExit(main(argv))